[Sherlock almost doesn't listen to the next refrain, too busy being disgusted at his own amateur rhyming in comparison. Nous and big house? Utterly deplorable. He's never called prison "the big house" in his life, that's a ridiculously American saying.

Not wanting to embarrass himself again, this time he actively resists the urge to join in and keeps himself apart from this odd song. At least there's no dance routine to go with it, small mercies.]

Hardly surprising that they'd turn to the lowest of their society, a common tactic for the day, but his alibi must have been strong indeed for them to release him. Such a vicious and prolonged stabbing suggests that the perpetrator knew the victim, frenzied attacks are usually the result of bottled up anger or resentment. Did the child attend classes, either with a governess or teacher, with any other children that she may have been outshining?

[It's most likely the work of an adult, but it would be stupid to rule out another child at this stage.]